刘烨课件微观经济学chapter_4

1、,Chapter 4,Individual and Market Demand,Chapter 4,Slide 2,Topics to be Discussed,Individual Demand P105 从第3章Consumer Choice 中推出 一种商品价格变动个人需求曲线 收入变动恩格尔曲线 （d的移动） Income and Substitution Effects P112 正常商品、低档商品、吉芬商品 Market Demand P117 水平相加得到,Consumer Surplus P122 Network Externalities P126 Empirical Est

2、imation of Demand P130,Chapter 4,Slide 3,Chapter 4,Slide 4,一、Individual Demand,Price Changes Using the figures developed in the previous chapter, the impact of a change in the price of food can be illustrated using indifference curves. 运用前几章学习的图形，通过无差异曲线，我们可以说明食品价格变化对需求产生的影响。,Chapter 4,Slide 5,Effec

3、t of a Price Change P106,Food (units per month),Clothing (units per month),Chapter 4,Slide 6,Price-Consumption Curve,Effect of a Price Change P106,Food (units per month),Clothing (units per month),4,5,6,U2,U3,A,B,D,U1,4,12,20,P105概念 The price-consumption curve traces out the utility maximizing marke

4、t basket for the various prices for food.,PF = $2, $1, $.50,Chapter 4,Slide 7,Effect of a Price Change P106由上图推出,Food (units per month),Price of Food,此时C的需求量如何变化？,Chapter 4,Slide 8,4.1 个别需求,个别需求曲线的两大特征 P106 1)当我们沿着需求曲线向下移动时，我们所能获得效用水平不断增加。 2）当我们沿着需求曲线下移时，食物对衣服的MRS逐渐下降。当消费者购买更多食物的时候，食物的相对价值便下降了。,个别需求

5、曲线,Chapter 4,Slide 9,价格变化的影响,食物数量,食物价格,Chapter 4,Slide 10,Individual Demand,Income Changes （P107） Using the figures developed in the previous chapter, the impact of a change in the income can be illustrated using indifference curves. 利用前几章学习的图形，收入变化对消费的影响可以通过无差异曲线表现出来,Chapter 4,Slide 11,Effects of I

6、ncome Changes P108,Food (units per month),Clothing (units per month),P107收入消费 曲线的概念,Assume: Pf = $1（不变） Pc = $2（不变） 偏好不变 I = $10, $20, $30,收入消费曲线并非就是一条直线！,Chapter 4,Slide 12,Effects of Income Changes P108,Food (units per month),Price of food,An increase in income, from $10 to $20 to $30, with the pr

7、ices fixed, shifts the consumers demand curve to the right.,I = $10, $20, $30,Chapter 4,Slide 13,4.1 个别需求,收入变化 收入消费曲线描述了在每一个收入水平下，使消费者效用实现最大化的衣服与食物的所有组合。 收入的增加使得预算线向右移动，沿着收入消费曲线向上，消费量也增加了。 同时，随着收入的增加，需求曲线也向右移动。,Chapter 4,Slide 14,Individual Demand,Income Changes When the income-consumption curve has

8、 a positive slope: The quantity demanded increases with income. The income elasticity of demand is positive. The good is a normal good.,Normal Good vs. Inferior Good P108,Chapter 4,Slide 15,Individual Demand,Income Changes When the income-consumption curve has a negative slope（如下图）: The quantity dem

9、anded decreases with income. The income elasticity of demand is negative. The good is an inferior good.,Normal Good vs. Inferior Good P108,Chapter 4,Slide 16,一种劣等商品 P109,汉堡包,牛排,收入消费曲线,但是，在B和C之间，收入消费 曲线向后弯曲，汉堡包就成了劣等商品。,Chapter 4,Slide 17,Effects of Income Changes P108,Food (units per month),Clothing

10、(units per month),An increase in income, with the prices fixed, causes consumers to alter their choice of market basket.,Assume: Pf = $1（不变） Pc = $2（不变） 偏好不变 I = $10, $20, $30,收入消费曲线并非就是一条直线！,Chapter 4,Slide 18,Individual Demand,Engel Curves恩格尔曲线 Engel curves relate the quantity of good consumed to

11、income. If the good is a normal good, the Engel curve is upward sloping.（还可分为必需品和奢侈品） If the good is an inferior good, the Engel curve is downward sloping.,Chapter 4,Slide 19,Engel Curves P110,Food (units per month),30,4,8,12,10,Income ($ per month),20,16,0,由P108图可推出本图,Chapter 4,Slide 20,Engel Curve

12、s P110,Food (units per month),30,4,8,12,10,Income ($ per month),20,16,0,可以需求收入弹性来划分,Consumer Expenditures in the United States P110,Entertainment70094712741514205426544300 Owned Dwellings1116172522533243445457939898 Rented Dwellings1957217023712536213715401266 Health Care1031169719181820205222142642

13、 Food2656338541094888542962208279 Clothing85997813631772177826143442,ExpenditureLess than1,000-20,000-30,000-40,000-50,000-70,000- ($) on:$10,00019,00029,00039,00049,00069,000and above,Income Group (1997 $),请见P111图示,Chapter 4,Slide 22,Individual Demand P111,1) Two goods are considered substitutes if

14、 an increase (decrease) in the price of one leads to an increase (decrease) in the quantity demanded of the other. e.g. movie tickets and video rentals 2) Two goods are considered complements if an increase (decrease) in the price of one leads to a decrease (increase) in the quantity demanded of the

15、 other. e.g. gasoline and motor oil,Substitutes and Complements,Chapter 4,Slide 23,Individual Demand,Substitutes and Complements If the price consumption curve is downward-sloping, the two goods are considered substitutes. If the price consumption curve is upward-sloping, the two goods are considere

16、d complements. 请回到P106图来看一下 They could be both! （P135复5）,Chapter 4,Slide 24,Price-Consumption Curve,Effect of a Price Change P106,Food (units per month),Clothing (units per month),4,5,6,U2,U3,A,B,D,U1,4,12,20,Substitutes and Complements,PF = $2, $1, $.50,Chapter 4,Slide 25,二、Income and Substitution

17、Effects P112,A fall in the price of a good has two effects: Substitution & Income Substitution Effect Consumers will tend to buy more of the good that has become relatively cheaper, and less of the good that is now relatively more expensive. Income Effect Consumers experience an increase in real pur

18、chasing power when the price of one good falls.,Chapter 4,Slide 26,Income and Substitution Effects,Substitution Effect The substitution effect is the change in an items consumption associated with a change in the price of the item, with the level of utility hold constant. When the price of an item d

19、eclines, the substitution effect always leads to an increase in the quantity of the item demanded.,Chapter 4,Slide 27,Income and Substitution Effects,Income Effect The income effect is the change in an items consumption brought about by the increase in purchasing power, with the price of the item he

20、ld constant. When a persons income increases, the quantity demanded for the product may increase or decrease. Even with inferior goods, the income effect is rarely large enough to outweigh the substitution effect.,Chapter 4,Slide 28,Income and Substitution Effects: Normal Good P113,Food (units per m

21、onth),O,Clothing (units per month),Chapter 4,Slide 29,Food (units per month),O,R,Clothing (units per month),F1,S,F2,T,A,U1,E,Substitution Effect,D,Income and SubstitutionEffects: Inferior Good P114,A Special Case: The Giffen Good P115,The income effect may theoretically be large enough to cause the

22、demand curve for a good to slope upward. This rarely occurs and is of little practical interest.,Chapter 4,Slide 31,Income and Substitution Effects,以上讲的主要是三种效应方向。那么它们大小如何?由何决定？P136复习题8,Chapter 4,Slide 32,Effect of a Gasoline Tax With a Rebate,Gasoline Consumption (gallons/year),Expenditures On Other

23、 Goods ($),Chapter 4,Slide 33,三、Market Demand,Market Demand Curves A curve that relates the quantity of a good that all consumers in a market buy to the price of that good.,From Individual to Market Demand,Chapter 4,Slide 34,Determining the Market Demand Curve,16101632 2481325 3261018 404711 50246,P

24、riceIndividual AIndividual BIndividual CMarket ($)(units)(units)(units)(units),Chapter 4,Slide 35,Summing to Obtain aMarket Demand Curve P117,Quantity,1,2,3,4,Price,0,5,5,10,15,20,25,30,Individual Market,1.横向相加水平相加 2. 市场需求曲线可能弯折斜率变化 提醒：不能简单相加（如P121），函数定义域，分段函数 3.P118 两个注意点 4.实质是部分需求加总成总需求,Chapter 4,

25、Slide 36,Chapter 4,Slide 37,Market Demand,Two Important Points P118 1)The market demand will shift to the right as more consumers enter the market. 2) Factors that influence the demands of many consumers will also affect the market demand.,Chapter 4,Slide 38,The Aggregate Demand For Wheat P121,Wheat

26、(million bushels/yr.),Price ($/bushel),0,2,4,6,8,10,12,14,16,18,20,1000,2000,3000,4000,练习题,1. 个别需求曲线与市场需求曲线有何不同？哪种曲线可能更具有价格弹性？ 2.对产品某种牌号（比如头领牌）滑雪板的需求和对所有牌号滑雪板的需求相比，哪种更具有价格弹性。,Chapter 4,Slide 39,Chapter 4,Slide 40,Market Demand (P119),Elasticity of Demand Recall: Price elasticity of demand measures t

27、he percentage change in the quantity demanded resulting from a 1-percent change in price.,Chapter 4,Slide 41,Price Elasticity andConsumer Expenditure P120,DemandIf Price Increases,If Price Decreases, Expenditures:Expenditures:,Inelastic (Ep 1) DecreaseIncrease,MARKET DEMAND,isoelastic demand curve D

28、emand curve with a constant price elasticity.,Unit-Elastic Demand Curve,When the price elasticity of demand is 1.0 at every price, the total expenditure is constant along the demand curve D.,Figure 4.11,Chapter 4,Slide 43,四、Consumer Surplus P122,Consumer Surplus 经济学原理中定义 The difference between the m

29、aximum amount a consumer is willing to pay for a good and the amount actually paid. 由Market Demand 到 Individual Demand,经济学原理中的图 需求曲线.,P,50,70,80,0,100,1,2,3,4,Q,可见，需求曲线高度代表了相应的（边际）买者的支付意愿,Chapter 4,Slide 45,Consumer Surplus 6 + 5 + 4 + 3 + 2 + 1 = 21,Consumer Surplus P123,Rock Concert Tickets,Price

30、($ per ticket),2,3,4,5,6,13,0,1,14,15,16,17,18,19,20,Chapter 4,Slide 46,4.4 消费者剩余,摇滚音乐会门票,实际支出,2,3,4,5,6,13,0,1,14,15,16,17,18,19,20,如果将商品的单位变得更小一些，楼梯型的需求曲线很容易地能够转变成一条直线型的需求曲线。,Chapter 4,Slide 47,Consumer Surplus,1、数量单位如无限可分，需求曲线则变成直线 2、需求曲线非直线下，同样适用。只是计算方法定积分 3、CS的衡量对个别需求曲线、市场需求曲线都适用，但含义有所不同。,Chapt

31、er 4,Slide 48,The Value of Clean Air,Air is free.Public Resource The Clean Air Act was established in 1977.限制排污 Question: Were the benefits of cleaning up the air worth the costs?,消费者剩余的应用：An Example P125,Chapter 4,Slide 49,The Value of Clean Air,People pay more to buy houses where the air is clean.

32、 Data for house prices among neighborhoods of Boston and Los Angeles were compared with the various air pollutants.,Chapter 4,Slide 50,Valuing Cleaner Air,Chapter 4,Slide 51,五、Network Externalities P126,Up to this point we have assumed that peoples demands for a good are independent of one another.（

33、相互独立的） If fact, a persons demand may be affected by the number of other people who have purchased the good. If this is the case, a network externality exists.,Chapter 4,Slide 52,Network Externalities,Network externalities can be positive or negative（P126） A positive network externality exists if the

34、 quantity of a good demanded by a consumer increases in response to an increase in purchases by other consumers. Negative network externalities are just the opposite.,Chapter 4,Slide 53,Network Externalities,攀比效应 The Bandwagon Effect positive network externality 之一种 如IPHONE、IPAD 它指的是一种赶潮流的欲望，想拥有一件几乎

35、其他人都有的商品，或者卷入时尚之中。 营销与广告活动的主要目标之一就是制造攀比效应（如玩具，服装的广告等等）。,Chapter 4,Slide 54,连带外部正效应: 攀比效应 P127,数量,价格,Chapter 4,Slide 55,Demand,Positive NetworkExternality: Bandwagon Effect P112,Quantity (thousands per month),Price ($ per unit),D20,20,40,60,80,100,D40,D60,D80,D100,Pure Price Effect,$20,48,Bandwagon E

36、ffect,在有攀比效应的情况 下市场需求弹性变大,$30,将需求曲线上相关点 连结起来就得到市场需求曲线。市场需求曲线相对富有弹性,Chapter 4,Slide 56,需求,连带外部正效应：攀比效应,数量,价格,D20,20,40,60,80,100,D40,D60,D80,D100,纯价格效应,48,假设价格从30美元下降到20 美元。如果不存在攀比效应， 那么，需求量仅增至48000。,$20,$30,Chapter 4,Slide 57,需求曲线,连带外部正效应：攀比效应,数量,价格,D20,20,40,60,80,100,D40,D60,D80,D100,纯价格效应,$20,48,

37、攀比效应,但是，由于更多的人购买了这种商品， 那么，拥有这种商品就成了一种时髦。 需求量进一步增加至80000。,$30,P128,网络正外部性的其他原因 电话、软件（如BT）、Email P129 Microsoft Windows PC operating system Fax-machines and e-mail,Chapter 4,Slide 58,Chapter 4,Slide 59,Network Externalities,虚荣效应 The Snob Effect Negative network externalities 之一种 The snob effect refers

38、 to the desire to own exclusive or unique goods.虚荣效应是指拥有唯我独尊的、独一无二的商品的欲望 The quantity demanded of a “snob” good is higher the fewer the people who own it.,Chapter 4,Slide 60,Negative NetworkExternality: Snob Effect,Quantity (thousands per month),Price ($ per unit),Chapter 4,Slide 61,Negative Network

39、Externality: Snob Effect,Quantity (thousands per month),2,4,6,8,存在虚荣效应下 会使得市场需求弹性变小。并抑制了价格下降 所产生的需求量的增加,Price ($ per unit),D2,$30,000,$15,000,14,D4,D6,D8,Demand,Pure Price Effect,Snob Effect,Net Effect,P129,网络负外部性的其他原因 最主要拥挤效应 例：游泳馆、溜冰场等,Chapter 4,Slide 62,Chapter 4,Slide 63,六、Empirical Estimation o

40、f Demand,The most direct way to obtain information about demand is through interviews where consumers are asked how much of a product they would be willing to buy at a given price.,Chapter 4,Slide 64,Empirical Estimation of Demand,Problem Consumers may lack information or interest, or be mislead by the interviewer. In direct marketing experiments, act